Who would have expected a programme about celebrities researching their ancestors could be such a hit with viewers?

Certainly not the BBC. Although they anticipated a little interest in Who Do You Think You Are? when it first broadcast in 2004, they didn’t foresee large audience figures, public acclaim, the desire for more and a format that would be snapped up by other broadcasters across the globe.

That opening run featured the likes of Vic Reeves, Jeremy Clarkson, Amanda Redman and Bill Oddie, while the second set focused on such luminaries as Sheila Hancock, Julian Clary and, best of all, a particularly moving insight into the family of Stephen Fry.

After such a long time on our screens, every time a new run is announced, viewers are left wondering who will be featured on it. After all this time and so many editions, some have suggested that the show must be running out of steam and that the celebrities will soon be Z-listers rather than bona fide stars.

However, the programme’s researchers keep coming up trumps - and if you need proof of that, check out the list of luminaries set to grace this, the 12th season.

“Who Do You Think You Are? is back with another fantastic line-up of much-loved faces, uncovering hidden history by bringing our celebrities’ ancestors to life,” says executive producer Colette Flight. “Following our best-known stars on their personal journey into their family trees reveals extraordinary stories, sometimes tragic, sometimes funny, but always compelling.”

As well as giving us a rare opportunity to see celebrities reveal their true personalities, the series also offers viewers a surreptitious history lesson - by delving into the past and finding out about the ancestors of the rich and famous, we also get a glimpse at what they did, how they lived and the morals of the time.

Of particular interest this time around will be Hall’s trip back in time, from her family’s roots in Oldham, Lancashire. She also discovers a link to American pioneering hero Daniel Boone.

Jacobi, meanwhile, uncovers humble tales from Walthamstow to the heady heights of the court of Louis XIV of France, as well as an ancestor who led a dangerous double life.

But first of all there’s an opportunity to see the usually stern Hollywood show a softer, more emotional side when he researches the military record of his maternal grandfather, Norman Harman, who was an anti-aircraft gunner during the Second World War.

“For me that was quite moving,” reveals the star baker. “I knew him and he was very close to me, but he rarely spoke about it.”

Expect more revelations and extraordinary stories over the next 10 weeks.